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Month November 2007

Learn how to combine JGoodies with other backend frameworks in your desktop application. The main problem is the need to create objects that extend the Model class while other frameworks might consider this a problem, either because they require POJOs or provide other specific rules.

If you create GUIs using the JGoodies Binding library, you will probably have to create bean classes that extend the com.jgoodies.binding.beans.Model class.

If your desktop application also uses a framework for other purposes (e.g., persistency) and you plan to use the same model object from the GUI with this framework, then you will have to make sure you don’t have conflicting requirements.

This problem is reasonably common and happens because java doesn’t allow multiple inheritance. So, any framework that is used in conjunction with JGoodies and has rules for the target object (e.g., it must be a POJO), then the implementation starts to become more complex.

Let’s discuss one possible solution for those cases where the other framework requires the object to be a POJO (e.g., Hibernate, JPA, etc.). In such cases, we can create one class for the POJO (attributes + getters + setters) and another class that wraps this POJO, which has similar methods but has the advantage to execute other actions.

This isn’t a perfect solution, but solves the problem. One disadvantage is the maintenance required by the two sets of methods that access the POJO, which could be automated by a small piece of code that uses java reflection.

This article explains the advantages of the Presentation Model pattern over the Model-View-Controller and Model-View-Presenter. This will improve your decisions about GUI implementations for desktop.

One of the major challenges in the development of desktop software is the effective use of unit tests that cover the GUI functionalities and its interactions with the remainder of the software. The complexity of this implementation lies in the control of selected items in lists and tables, modal dialogs, clicks and events. In fact, it is extremely difficult to develop good tests on the GUI when the application logic is tightly-coupled to UI components.

You probably have already heard about design patterns that could help in this case, especially those that separate the application logic from UI components. Perhaps the most famous is the Model-View-Controller (MVC), which has been widely used not only for desktop applications but also for web development.

There is a relevant question that we should ask ourselves at this point: Is this separation between logic and UI components enough to reduce the complexity of writing GUI unit tests?

Figure 1 presents the three most important presentation patterns for desktop development. Besides the MVC, there is one called Model-View-Presenter (MVP) that consists of a small variation of the first one (see Martin Fowler’s description of them for more details).

Figure 1: Patterns for desktop application development.

The important thing to notice in this picture is that both MVC and MVP describe the controller/presenter with a reference to the view. So, to create an instance of the controller inside the test code, we need the view as well. This still makes the development of unit tests difficult.

There is a turnaround to this problem, which is basically to add an interface between the controller and the view to break this dependency and abstract the view’s components. But the idea behind this solution increases the amount of code and does not imply in less complexity and clean organization. In most of the cases, this resolution is not worth the effort when there is a third option such as the Presentation Model pattern.